The present invention relates to automatic adjustment of frequency response characteristics of a tape recorder for providing a flat response to audio signals recorded in the tape.
It is known that magnetic recording tapes exhibit different magnetic characteristics due to slight differences in material coated on the base of the tape. Due to the different magnetic characteristics, optimal bias level and frequency response characteristics also differ between tapes. The different characteristics require the user to adjust the bias level and equalizer characteristics of the tape recorder whenever the recording tape is replaced. Automatic bias level setting is accomplished in a manner as disclosed in copending United States Patent Application Ser. No. 24,875, filed Mar. 28, 1979, now U.S. Pat. No. 4,220,979 which the bias level is swept across in a given range and recorded in a tape prior to an actual recording operation. The recorded bias is reproduced to determine the optimal level which minimizes waveform distortion.
Although the distortion factor may be reduced to a minimum, the different signal level and frequency characteristics are still reflected in the reproduced signal. If the tape recorder is provided with a noise reduction system having nonlinear compression-expansion characteristics the replacement of tapes would result in a deviation of the actual characteristic from the desired one, and hence a loss of faithful reproduction.